Sheet stacking apparatus

ABSTRACT

Apparatus for stacking sheets with end edges of the sheets substantially aligned and in a vertical plane. The apparatus includes a pair of elongated, laterally spaced, powerdriven conveyor belts engaging the top faces of the sheets, and skate roller support means supporting the bottom faces of the sheets. The conveyor belts are independently driven, and each may be stopped independently of the other in producing alignment of a sheet. The skate roller support means are moved out from under a sheet to free a sheet for dropping onto a stack.

United States Patent Russell et al.

1451 July 11,1972

[54] SHEET STACKING APPARATUS [72] inventors: Phillips 6. Russell, Alsea; Leon E. Guggenbickler, Albany; John H. Crawford, Corvallis, all of Greg.

[73] Assignee: Brand S Corporation, Corvallis, Oreg.

[22] Filed: Nov. 16, 1970 [21] Appl. No.: 89,745

[52] US. Cl ..2l4/6 DK, 271/50, 271/68 [5 1] Int. Cl ..B65g 57/00 [58] Field at Search ..27l/50, 68; 214/6 DK, 6 P, 214/6 G, 6 H, 6 D

[56] References Cited UNITED STATES PATENTS 2,733,921 2/ 1 956 Downs ..214/6 DK 2,752,051 6/1956 Strahm et a] ..214/l6.l CB

3,447,695 6/ 1969 Krepp et a] ..2i4/6 DK 3,044,767 7/ I962 Winkler et al. ..27l/50 X FOREIGN PATENTS OR APPLICATIONS 1,083,180 6/1960 Germany ..214/6 DK Primary Examiner-Robert J. Spar Anomey-Kolisch & Hartwell ABSTRACT Apparatus for stacking sheets with end edges of the sheets substantially aligned and in a vertical plane. The apparatus includes a pair of elongated, laterally spaced, powerdriven conveyor belts engaging the top faces of the sheets, and skate roller support means supporting the bottom faces of the sheets. The conveyor belts are independently driven, and each may be stopped independently of the other in producing alignment of a sheet. The skate roller support means are moved out from under a sheet to free a sheet for dropping onto a stack.

6Clains,3DrawlngFigures PATENTEUJUL 1 1 1972 SHEET 10F 2 JNVENTORS 14% i" Z s Phillip G. Russel] Leon E.Guggenbickler John Hfrawford fi/d-wh 4am SHEET STACKING APPARATUS This invention relates to apparatus for stacking sheets, and more particularly to apparatus which will stack sheets with corresponding end edges of the sheets in the stack substantially aligned.

In the handling of sheets, such as sheets of veneer used in plywood manufacture, it is often necessary to take sheets from a conveyor and stack them with at least one edge of each sheet in the stack aligned with a similar edge in each of the other sheets in the stack. One way in which this has been accomplished in the past is by removing the sheets from the conveyor and depositing them on the stack by hand. Not only is this slow, but there is also a tendency for sheets to tear or break when pulled from the conveyor. Other methods which have been used include moving the sheets along a conveyor until they hit a stationary fence and then dropping the sheets from the conveyor, or dropping the sheet from the conveyor with some movement in the direction of the edge to be aligned, with that edge then hitting against a fence in the stacking region. It should be apparent that such stopping of moving sheets by hitting against stationary fences results in considerable edge damage.

A general object of the invention is to provide novel apparatus for stacking sheets with corresponding edges aligned in the stack, which handles the sheets rapidly and with minimum damage.

Another object is to provide such apparatus where sheets are conveyed along a path, the position of an edge in a sheet is detected and sheet-positioning movement is undertaken if this edge is improperly positioned, and after such positioning movement the sheet is dropped from the conveyor onto the forming stack.

Another and more specific object of the invention is to provide such stacking apparatus wherein a pair of endless belt conveyors function to convey the sheet, such belts being laterally spaced apart from each other and their bottom reaches engaging the top faces of the sheets being conveyed. A pair of laterally spaced skate roller support means support theundersides of sheets being conveyed by such belt conveyors. On dropping of a sheet these skate roller support means are readily moved out from under the sheet with the rollers skidding off the edge margins of the sheet.

A related object is to provide such apparatus where the positioning of a sheet is through manipulation of the endless conveyor belts, i.e., by controlling the relative speed at which the two conveyor belts run.

These and other objects and advantages will become more fully apparent as the following description is read in conjunction with the drawings, wherein:

FIG. 1 is a side elevation of a portion of a veneer sorting system including stacking apparatus according to the invention;

FIG. 2 is an end elevation of the stacking apparatus of the invention taken generally along the line 2-2 in FIG. 1; and

FIG. 3 is a top plan view of the stacking apparatus taken generally along the line 33 in FIG. 1.

Referring to FIG. 1, here a sorting line is shown with portions of three different stackers shown at 2, 4, and 6, for stacking veneer as such is sorted.

The sorting line includes a frame on which are mounted a series of horizontal power-driven belt conveyors l2, l4, 16. The belt conveyors are driven in such a direction that their upper work-supporting reaches move to the left in FIG. 1, whereby they may move sheets of veneer 20, or other sheet material, to the left in FIG. 1.

Pivotally mounted between the upstream end of conveyor 12 and the downstream end of conveyor 14, and between the upstream end of conveyor 14 and the downstream end of conveyor 16, are skate roller conveyor sections 24, 26, respectively. The conveyor sections are pivotally mounted on frame 10 for swinging between a horizontal or sheet-carrying position, as illustrated by section 24, and a diverting position, as illustrated by section 26. In a sheet-carrying position, a conveyor 7 section forms a bridge over which veneer sheets travel from one belt conveyor to the next. In a diverting position, the upstream end of the skate roller conveyor section is raised above the plane of the belt conveyors and is operable to divert a sheet, such as that indicated at 30, from a belt conveyor and direct such onto an inclined skate roller conveyor section, such as that shown at 34. The latter guides a sheet into a stacker or stacking apparatus.

The stackers are similar, and only one will be described in detail.

Referring now to FIGS. 1, 2, and 3, stacking apparatus 4 includes a pair of elongated, parallel, laterally spaced, endless conveyor belts, or elements, 48, 50. The belts are supported with their lower reaches substantially horizontal.

As seen in FIGS. 1 and 2, belt 50 is driven through a shaft 52, sprockets 56, 58, and a drive chain 60, by an electric motor 62. Interposed between motor 62 and sprocket 58 is a conventional clutch-brake mechanism 66. With the clutch engaged, the brake is released and the motor is drivingly coupled to sprocket 58. With release of the clutch, the brake engages to disconnect the motor and brake rotary movement of the sprocket.

A similar drive means is provided for belt 48, including electric motor 68 and clutch brake mechanism 70.

The drive means described constitutes an adjustable drive means, whereby either belt may be left running with the other one stopped, the running belt having a faster running speed in a relative sense than the stopped belt. It is through such control of belt movement that sheet positioning is accomplished, as will be hereinafter described.

In each stacker, or stacking apparatus, a pair of elongated skate roller support means, or elements, are provided, with one of such support means normally underlying each of the conveyor belts. In apparatus 4, such skate roller support means are exemplified by support means 74 and support means 76 under conveyor belts 48, 50, respectively. Each support means includes rollers, such as those shown at 78, journaled on an elongated mounting bar 80. Upper sides of the rollers occupy substantially a common plane, and the rollers define a supporting plane for a veneer sheet pressed thereagainst by an overlying conveyor belt.

Each roller support means is mounted on the lower extremities of a pair of spaced-apart C-shaped members 84. Upper extremities of member 84 are secured to a rotatable shaft 86 which is joumaled for rotation about an axis that substantially parallels the belts.

The shafts 86 associated with the roller support means on either side of the stacker are interconnected for simultaneous rotation by a tie rod 90. The connection is such that the rotations of spaced shafts 86 are in opposite directions. Powering such rotation of the shafts is a fluid-operated ram 94. When the ram 94, and referring to FIG. 2, is extended the skate roller support means supporting opposite side margins of a sheet are caused to be moved downwardly and laterally outwardly until finally the sheet is free of the support means and drops. The smooth-surfaces skate rollers slide easily out from under the sheet with minimal disruption of sheet position.

Referring to FIG. 3, shown at 104 and 106 are a pair of limit switches, having actuators for the switches which are in the path of travel of veneer moving along under belts 48, 50. The switches are aligned in a direction extending normal to the belts 48, 50. One switch is adjacent one belt, and thus one side of the veneer sheet moving under the belt, and the other is adjacent the other belt and the other side of the veneer sheet. Switches 104, 106 are part of a conventional control circuit provided to control operation of clutch-brake mechanisms 70, 66, respectively.

Explaining how the switches control operation of these clutch-brake mechanisms and the movement of a sheet, in the absence of any sheet under belts 48, 50, the two switches are in one state, the clutches of the clutch-brake mechanisms are engaged, and the brakes of the clutch-brake mechanisms are disengaged. Drive is transmitted from both motors 62, 70 to the belts 50, 48. On a sheet traveling forwardly under the urging of belts 48, 50, and assuming its lead edge is normal to the belts, which is the proper position desired, and upon such lead edge striking the actuators for the switches, both switches are substantially simultaneously adjusted to another state. With the switches in this other state, the clutches in the clutch plate mechanisms are disengaged and the brakes in these mechanisms engaged, with stoppage of movement in the belts resulting. With both switches in this other state, a circuit for ram 94 is also actuated causing it to extend, whereby the skate roller support means are caused to move out from under the veneer sheet. With the sheet having dropped, and after a predetermined time interval, the circuit becomes reinstated in its original condition with switches 104, 106 in their original state, skate roller support means 74, 76 underlying belts 48, 50, and drive transmitted from the motors 62, 70 to the belts.

Should there be skewing in a sheet so that its lead edge is not substantially normal to the belts, one switch will be adjusted to its other state prior to such adjustment taking plate in the other switch. That switch which is actuated first will cause movement of that belt, which is associated with that switch to be stopped, and this occurs with no interruption in the movement of the other belt. This other belt, in other words, continues to run, and thus has a faster running speed than the first mentioned belt which is stopped. This differential in belt movement causes the sheet to turn, whereby its leading edge is shifted to a position normal to the belts and the path of sheet travel. On reaching this position, the other switch finally becomes actuated to stop movement of the other belt, and the sheet is dropped.

The switches, therefore, in performing the various functions outlined above, constitute sensing means in the organization which sense the skewing of a sheet from a predetermined desired position, which is a position where its leading edge is normal to the direction the sheet travels. Having sensed any such skewing, it controls the adjustable drive means to produce a corrective positioning of the sheet. After such positioning, the sheet is dropped from the stacking apparatus with its leading edge in proper position. Successive sheets are similarly positioned and dropped with their leading edges becoming aligned with each other in the forming stack.

Positioned below the skate roller support means is a scissor lift platform 110 which receives sheets dropped from the skate roller support means. The scissor lift platform is of conventional construction, and includes operating mechanism providing for successive lowering of the platform as sheets of veneer are added to a stack 1 11 thereon. In this way, the top of the stack is maintained at a substantially constant distance below belts 48, 50 and the skate roller support means.

Depending from bars 80 of the skate roller support means are elongated plates 112, 114, also referred to herein as side edge aligning means. These plates, with the skate roller support means in the position shown in solid outline in FIG. 2, are spaced from each other a distance which is substantially equal to the width of the fonning stack. On the skate roller support means returning to the position shown in F IG. 2 after dropping a sheet, plates 112, 1 14, strike any side edges of the sheet that overly protrude from stack 111 to shift this side edge toward alignment with corresponding side edges of other sheets in the stack, thus to produce a corrective positioning of such sheet.

The operation of the sorting line, including the stacker as illustrated, should be obvious from the above description. Very briefly, sheets traveling along belt conveyor 16 on being diverted to stacker 4 move forwardly into the stacker while held between belts 48, 50 and the underlying skate roller support means. Prior to being dropped, any skewing of the sheet from the desired position is detected by switches 104, 106, and corrective positioning is applied to the sheet where necessary. Sheets are dropped out from under the conveyor belts 48, 50 to form a stack where the leading edges of the sheets are substantially aligned. Further corrective positioning of the sheets in the forming stack is performed by the side plates 112, l 14 described.

It should be obvious that the apparatus described has a number of advantages over existing approaches. The machine is rapid and reliable in its operation. Sheets are handled carefully and without the application of such forces as would cause breaking or other damage. An aligning operation is performed, not only with respect to the leading edges of sheets, but also of both side edges. Further, with a sheet being gripped between the conveyor belts and the skate roller support means, a sheet which may have a tear extending thereacross laterally of the path will be held together as it is conveyed through the stacking apparatus and will be dropped onto the stack with the severed portions retained substantially in proper relationship to each other facilitating subsequent repair.

While a specific embodiment of the invention has been described, it should be apparent to those skilled in the art that various changes and modifications are possible without departing from the spirit of the invention.

It is claimed and desired to secure by Letters Patent:

1. Apparatus for stacking sheets comprising a pair of laterally spaced, elongated, power-driven conveyors operable to engage a sheet adjacent opposite side edges and to move it along a substantially horizontal path, each conveyor including a belt engaging the top face of a sheet and an elongated support means supporting the underside of the sheet,

adjustable drive means for driving the conveyors enabling selectively either conveyor to have a faster running speed than the other, and

release means for moving said support means laterally outwardly beyond the side edge of the sheet for releasing such sheet from said conveyors to deposit the sheet in a stacking region therebelow.

2. The apparatus of claim 1, which further comprises sensing means, operable to sense the alignment of a sheet, controlling the adjustable drive means.

3. The apparatus of claim 1, wherein said adjustable drive means comprises motor means, and a clutch and brake combination for each conveyor for connecting the motor means to the conveyor.

4. Apparatus for stacking sheets comprising a pair of elongated, laterally spaced skate roller support means for supporting opposite side margins of the sheets being stacked a pair of continuous conveyor belts mounted with the lower run of one belt over one skate roller support means and the lower run of the other belt over the other skate roller support means,

motor means and adjustable coupling means coupling said motor means to the belt enabling either belt selectively to be disconnected from the motor means,

sensing means sensing the alignment of a sheet deposited on said skate roller support means for controlling said coupling means,

movable support arms mounting each skate roller support means shiftable to swing the skate roller support means laterally of a sheet to permit the same to fall freely therefrom, and

power-operated means connected to said support arms for each skate roller support means for powering movement of the support arms.

5. Apparatus for stacking sheets comprising a pair of laterally spaced, elongated conveyors operable to engage a sheet adjacent opposite side edges and to move it along a substantially horizontal path, each conveyor including a power driven conveyor element for frictionally engaging a horizontal face of a sheet and on operation urging such sheet to move along said path, and a support element for bearing against the opposite horizontal face of the sheet to hold the same in contact with the conveyor element,

adjustable drive means for driving the conveyor elements of the conveyors enabling selectively either conveyor to have a faster running speed than the other, and

release means for releasing such sheet from said conveyors to deposit the sheet in a stacking region therebelow. 6. The apparatus of claim 5, wherein one of said elements in a conveyor is positioned to engage the underside of a sheet and said release means comprises means for moving said ele- 5 ment laterally outwardly beyond a side edge of the sheet.

I! l I! 

1. Apparatus for stacking sheets comprising a pair of laterally spaced, elongated, power-driven conveyors operable to engage a sheet adjacent opposite side edges and to move it along a substantially horizontal path, each conveyor including a belt engaging the top face of a sheet and an elongated support means supporting the underside of the sheet, adjustable drive means for driving the conveyors enabling selectively either conveyor to have a faster running speed than the other, and release means for moving said support means laterally outwardly beyond the side edge of the sheet for releasing such sheet from said conveyors to deposit the sheet in a stacking region therebelow.
 2. The apparatus of claim 1, which further comprises sensing means, operable to sense the alignment of a sheet, controlling the adjustable drive means.
 3. The apparatus of claim 1, wherein said adjustable drive means comprises motor means, and a clutch and brake combination for each conveyor for connecting the motor means to the conveyor.
 4. Apparatus for stacking sheets comprising a pair of elongated, laterally spaced skate roller support means for supporting opposiTe side margins of the sheets being stacked a pair of continuous conveyor belts mounted with the lower run of one belt over one skate roller support means and the lower run of the other belt over the other skate roller support means, motor means and adjustable coupling means coupling said motor means to the belt enabling either belt selectively to be disconnected from the motor means, sensing means sensing the alignment of a sheet deposited on said skate roller support means for controlling said coupling means, movable support arms mounting each skate roller support means shiftable to swing the skate roller support means laterally of a sheet to permit the same to fall freely therefrom, and power-operated means connected to said support arms for each skate roller support means for powering movement of the support arms.
 5. Apparatus for stacking sheets comprising a pair of laterally spaced, elongated conveyors operable to engage a sheet adjacent opposite side edges and to move it along a substantially horizontal path, each conveyor including a power driven conveyor element for frictionally engaging a horizontal face of a sheet and on operation urging such sheet to move along said path, and a support element for bearing against the opposite horizontal face of the sheet to hold the same in contact with the conveyor element, adjustable drive means for driving the conveyor elements of the conveyors enabling selectively either conveyor to have a faster running speed than the other, and release means for releasing such sheet from said conveyors to deposit the sheet in a stacking region therebelow.
 6. The apparatus of claim 5, wherein one of said elements in a conveyor is positioned to engage the underside of a sheet and said release means comprises means for moving said element laterally outwardly beyond a side edge of the sheet. 